1. Field of the Invention
The present invention relates to an exhaust system for a watercraft, and more particularly to cooling system for an exhaust system of a watercraft.
2. Description of Related Art
Personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and carries a rider and possibly one or two passengers. A relatively small hull of the personal watercraft commonly defines a riders"" area above an engine compartment. A two-cycle internal combustion engine frequently powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on the underside of the watercraft hull. The jet propulsion unit is located within the tunnel and is driven by a drive shaft. The drive shaft usually extends between the engine and the jet propulsion device, through a wall of the hull that forms a front gullet portion of the tunnel.
An exhaust system of the personal watercraft discharges engine exhaust to the atmosphere either through or close to the body of water in which the watercraft is operating. Although submerged discharge of engine exhaust silences exhaust noise, environmental concerns arise. These concerns are particularly acute in connection with two-cycle engines because engine exhaust from two-cycle engines often contains lubricants and other hydrocarbons.
Such environmental concerns have raised a desire to minimize exhaustion of hydrocarbons and other exhaust byproducts (e.g., carbon monoxide and oxides of nitrogen) and thus reduce pollution of the atmosphere and the body of water in which the watercraft is operated. In response to the increased concerns regarding exhaust emissions, several outboard motors recently have become equipped with a catalyst to convert exhaust byproducts to harmless gases.
Catalysts must operate at a relatively high temperature in order to the necessary thermal reaction and burning of the exhaust byproducts. A catalyzer thus desirably operates within a specific range of temperature so as to effectively and efficiently convert engine exhaust into generally harmless gases.
One aspect of the present invention involves a cooling system for an exhaust system including a catalyzer. The cooling system regulates the temperature of the catalyzer within a desired range of operating temperatures. For this purpose, the cooling system desirably supplies coolant to a cooling jacket around the catalyzers independent of an engine cooling system.
In one application of the present invention, a small watercraft, such as a personal watercraft, is provided with an internal combustion engine. The engine includes at least one exhaust port and an output shaft which drives a propulsion device. An exhaust system extends between the engine exhaust port and a discharge port, and includes a catalyzer to treat exhaust gases from the engine before discharge through the exhaust port. A cooling jacket extends along a portion of the exhaust system in the vicinity of the catalyzer. A coolant supply system communicates with the cooling jacket independent of the engine to cool the catalyzer.
Another aspect of the present invention involves a watercraft comprising an internal combustion engine. The engine has at least one exhaust port and an output shaft which drives a propulsion device. An exhaust system extends between the engine exhaust port and a discharge port, and includes a catalyzer to treat exhaust gases from the engine before discharge through the exhaust port. A cooling jacket extends along a portion of the exhaust system in the vicinity of the catalyzer. A coolant supply system communicates with the cooling jacket and with a source of fresh coolant to directly supply fresh coolant to the cooling jacket.
In accordance with an additional aspect of the present invention, a watercraft is provided having an internal combustion engine disposed within a hull of the watercraft. The engine has at least one exhaust port which communicates with an exhaust system that delivers engine exhaust to a discharge port. A cooling jacket extends along a portion of the exhaust system. The watercraft also includes a bilge system having a bilge pump. The bilge pump communicates with the cooling jacket to pump bilge water from a bilge area of the hull to the cooling jacket to provide additional cooling of the portion of the exhaust system.
Another aspect of the present invention involves a watercraft comprising an internal combustion engine having at least one exhaust port and an output shaft. A jet propulsion device propels the watercraft and is driven by the engine output shaft. An exhaust system extends between the engine exhaust port and an exhaust discharge outlet to discharge exhaust gases from the watercraft. The watercraft also includes an upwardly spraying water discharge nozzle and a water cooling system. The water cooling system includes a water jacket and water supply system which receives water from the jet propulsion unit. The water supply system communicates with both the water jacket and the discharge nozzle, and includes a flow regulator which controls the water flow to the water jacket and to the discharge nozzle.
In accordance with a further aspect of the present invention, a watercraft comprises an internal combustion engine having at least one exhaust port and an output shaft. A jet propulsion device is driven by the engine output shaft to propel the watercraft. An exhaust system extends between the engine exhaust port and an exhaust outlet to discharge exhaust gases from the watercraft. The exhaust system includes at least one water jacket that extends along at least a portion of the exhaust system""s length. The watercraft also includes an upwardly spraying water discharge nozzle and a water supply system which communicates with both the discharge nozzle and the exhaust system water jacket. The water supply system receives water from the jet propulsion unit and communicates with the water jacket independent of the engine.
Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follow.